Today I learned, that one can burn candles to produce oxygen. Of course not your every day candles but so-called chlorate candles, which are made of sodium chlorate and iron powder. The iron powder is then enlightened to burn at around 600°C producing sodium chloride, iron oxide and oxygen. The key is, that the oxidization of the iron powder frees more oxygen from the sodium chlorate than it needs resulting in a positive oxygen output.
I came across this while watching this episode of “Smarter Every Day” talking about how nuclear submarines produce oxygen while staying under water for weeks.